The proposed research involves a prospective study of street crime. Comparisons will be made between acts of crime committed by persons under the influence of illicit drugs and acts of crime committed by persons not under the influence of drugs. The work will be assisted by the Drug Enforcement Administration, which will identify areas of New York City where illicit drug use is prevalent, and the New York City Police Department Street Crime Unit, which will position the principal investigator at sites where street crime can be witnessed. During the proposed study, an estimated 100-125 crimes will be witnessed. For each crime, the data that will be collected include: 1.) a tape recorded description, 2.) a data sheet that includes causes of arrest and suspects' claims concerning illicit drug use, and 3.) a urine analysis. The study will be conducted without endangering the rights of suspects; there will be no entrapment and no violation of ethics. The proposed study should permit a determination of whether illicit drug use influences the manner in which street crimes are committed.